Justified text is what a book looks like in most people's heads: two clean vertical edges, the block of type sitting square on the page. So it gets switched on early, and then the page develops a problem the writer can see but not name.
The problem is that justification is not free. Something has to give to make every line end at the same point, and what gives is the space between the words.
What justification actually does
A line of type is set with a natural word space. To justify it, the typesetter takes the leftover room at the end of the line and distributes it into the spaces between the words. On a line that was nearly full, that is a fraction of a millimetre per gap and nobody notices. On a line that was half empty — because the next word was long and would not fit — it can be several times the natural space.
- Rivers. When wide spaces on consecutive lines happen to align vertically, the eye connects them into a pale channel running down the paragraph. Once you have seen one you cannot unsee it.
- Loose lines. A single line stretched so far that it reads as a different typeface from the one above it.
- Tight lines. The opposite fault, where the engine squeezes instead, and words start to touch.
Hyphenation is the fix, not a compromise
Justification and hyphenation are one feature, not two. Hyphenation lets a long word break across a line ending, which means the typesetter has far more places to put the line break and far less leftover space to absorb. Every professionally set justified book on your shelf is hyphenated, and the hyphens are invisible to you because they are doing their job.
This is why justified text looks wrong in so many self-published books and in so many browsers: the alignment is on and hyphenation is off. Web browsers historically did not hyphenate by default, which taught a generation of people that justified text looks bad. It does not. Unhyphenated justified text looks bad.
| Setting | Result |
|---|---|
| Justified, hyphenated, wide measure | What a printed book looks like |
| Justified, no hyphenation | Rivers and loose lines. Avoid |
| Justified, narrow measure | Bad even with hyphenation — too few words per line |
| Ragged right, any measure | Always safe. Even word spacing, uneven right edge |
The measure decides it
The real variable is how many words are on a line. Justification works by borrowing a little space from many gaps; with only six or seven words on a line there are not enough gaps to borrow from, so each one has to give up more.
As a working threshold: justify above about 60 characters a line, set ragged right below about 45, and use your judgement between them. Margins and line length covers how to get the measure into that range in the first place, which is the more fundamental decision — the alignment follows from it.
Which is why a two-column layout is almost always ragged right, and why a novel at 6×9 inches is almost always justified. The layout chose the alignment before anyone had an opinion about it.
Where ragged right is simply correct
- Anything reflowable. An EPUB is repaginated on a device you have never seen at a type size you did not choose, so you cannot know the measure. Leave ebook text ragged and let the reading system decide.
- Narrow columns. Workbooks, sidebars, marginal notes, anything in two columns.
- Poetry. Lines end where the poet put them; verse has its own rules entirely.
- Lists, captions, tables. Short strings have nowhere to absorb the space.
- Headings. Never justify a heading. A two-line heading stretched to the full measure is unmistakably wrong.
- Text in a language you are not hyphenating. German and Finnish compound words are long; without hyphenation, justified setting in either is unreadable.
Never justify the last line, and other details
Three refinements that separate careful setting from a checkbox:
- The last line of a paragraph is never justified. It ends where it ends. Any tool that stretches it across the full measure is broken; this is called force-justification and it is only ever correct on a single-line display heading.
- Avoid a runt — a last line holding one short word. Fix it by editing the sentence, the same way you would fix a widow.
- Limit consecutive hyphens. Three hyphenated line endings in a row starts to be visible. Traditional practice caps it at two.
And do not centre body text. Centring is for a title page, a dedication or an epigraph — three or four lines at most. Centred paragraphs have two ragged edges, so the eye has no reliable place to start each line, and a page of it is genuinely tiring to read.
So which do you pick?
If you are making a PDF at a normal book measure and your tool hyphenates, justify — it is the convention, and conventions in book design are mostly accumulated evidence about what is comfortable to read. If your tool does not hyphenate, or the column is narrow, or the file is an EPUB, set it ragged right and stop thinking about it.
The mistake worth avoiding is switching justification on because it looks more booklike and then never checking a printed page. Look at a real spread, defocus, and see whether the texture is even. That check takes ten seconds and it is the whole decision. The sample book is eight pages of what even texture looks like at a normal measure.